Height adjustment cylinder with non-tapered threaded region

Abstract

A height adjustment cylinder for use with a desk chair, where the cylinder is simple, reliable and easily assembled with the chair. The cylinder includes a piston shaft which has a threaded region that is of constant diameter or straight walled, and the threaded region includes a high load helical thread.

1 . A height adjustment cylinder with a non-tapered threaded shaft comprising: 
 an elongated housing; and    a piston movable in said housing, said piston having a piston head completely enclosed by said housing and a shaft extending partially in said housing and partially out of said housing, said shaft having an end portion extending away from said housing, said shaft having a substantially constant diameter with a screw thread formed on said end portion, and a shoulder formed adjacent to said screw thread to limit the axial insertion of the said portion into a chair hub.    
   
   
       2 . The apparatus as claimed in  claim 1  wherein: 
 said screw thread includes a high load helical thread.    
   
   
       3 . A height adjustment assembly for a chair comprising: 
 a cylinder having a tubular shape with an inner surface, an outer surface, a closed lower end portion and an open upper end portion; and    a piston movable within said cylinder in a reciprocal manner, said piston including a piston head totally enclosed by said cylinder and a rod connected to the piston head and extending away therefrom, said piston head being movable along the inner surface of said cylinder and said rod extending out of said open upper end portion of said cylinders, said rod having a substantially constant cross section, with a non-threaded portion, a threaded end portion and a shoulder separating said threaded end portion from said non-threaded portion.    
   
   
       4 . The height adjustment assembly of  claim 3  wherein: 
 said threaded end portion includes a high load helical thread.    
   
   
       5 . The height adjustment assembly of  claim 3  wherein: 
 the diameter of said threaded end portion of said rod is substantially constant and is non-tapered.    
   
   
       6 . The height adjustment assembly of  claim 5  wherein: 
 said threaded end portion includes a high load helical thread.    
   
   
       7 . An adjustable, swivel chair assembly comprising: 
 a seat;    a back connected to said seat;    a base for supporting said seat and said back;    an adjustable column mounted to said base; and    a hub mounted under said seat, said adjustable column including a cylinder and a piston movable within said cylinder in a reciprocal manner, said piston including a piston head totally enclosed by said cylinder and a rod connected to the piston head and extending away therefrom, said rod having a substantially constant cross section, with a non-threaded portion, a threaded end portion and a shoulder separating said threaded end portion from said non-threaded portion, said threaded end portion being threadedly engaged with said under seat mounted hub such that said shoulder of said rod contacts said hub.    
   
   
       8 . The chair of  claim 7  wherein: 
 said cylinder has a tubular shape with an inner surface, an outer surface, a closed lower end portion and an open upper end portion.    
   
   
       9 . The chair of  claim 8  wherein: 
 said piston head is movable along said inner surface of said cylinder.    
   
   
       10 . The chair of  claim 8  wherein: 
 said rod extends out of said open upper end portion of said cylinder.    
   
   
       11 . The chair of  claim 10  wherein: 
 said piston head is movable along said inner surface of said cylinder.    
   
   
       12 . The chair of  claim 11  wherein: 
 said threaded end portion of said rod includes a high load helical thread.    
   
   
       13 . The chair of  claim 7  wherein: 
 said threaded end portion of said rod includes a high load helical thread.    
   
   
       14 . The chair of  claim 13  wherein: 
 said rod extends out of an open upper end portion of said cylinder.    
   
   
       15 . The chair of  claim 7  wherein: 
 said hub includes an opening and at least one set screw for engaging said rod.    
   
   
       16 . The chair of  claim 15  wherein: 
 said rod extends out of an open upper end portion of said cylinder.    
   
   
       17 . The chair of  claim 16  wherein: 
 said threaded end portion of said rod includes a high load helical thread.    
   
   
       18 . A method for assembling an adjustable swivel chair comprising the steps of: 
 providing a chair seat;    providing a chair back;    providing a chair base;    providing a chair column, wherein said column includes a cylinder and a piston and said piston includes a piston head totally enclosed by said cylinder and a rod, and said rod having a non-threaded portion, a non-tapered, threaded end portion and a shoulder;    attaching said column to said base;    providing an under seat hub;    attaching said hub to said seat; and    inserting said threaded end portion of said rod into said hub until said shoulder engages said hub.    
   
   
       19 . The method of  claim 19  wherein: 
 said threaded end portion includes a high load helical thread.    
   
   
       20 . The method of  claim 19  wherein: 
 said hub includes a threaded opening and a set screw positioned adjacent said opening; and    including the steps of:    engaging said threaded end portion of said rod with the hub through said threaded opening; and    engaging said threaded end portion of said rod with said set screw.